The present invention relates to a golf ball excellent in flight performance.
It is a well-known fact that a golf ball should have a high rebound resilience and a low aerodynamic resistance attributable to dimples arranged on its surface so that it flies over a long distance after hitting. For reduction of aerodynamic resistance, there have been proposed several methods for arranging dimples on the ball surface as densely and uniformly as possible.
As shown in FIG. 7, a golf ball (G) usually has dimples (s) which are circular dents as viewed from above. For such circular dimples (s) to be densely arranged, it is necessary to narrow down the flat part or land (t) separating adjoining dimples from each other. Even though the flat part or land (t) is infinitely narrow, there still exists a triangular or rectangular flat part of certain size in the area surrounded by three or four dimples. On the other hand, it is essential to arrange dimples as uniformly as possible on the ball's spherical surface. This necessitates making a compromise between the density and the uniformity of dimple arrangement.
One conventional way to achieve the object of arranging dimples densely and uniformly was to arrange two to five kinds of dimples differing in diameter assuming that the ball's spherical surface is a polyhedron (e.g., regular octahedron or icosahedron).
However, as far as dimples are circular, the total area of dimples practically accounts for only 75% or so in the surface area of the sphere, with the remainder (25%) being the area of flat parts or land.
On the other hand, U.S. Pat. No. 6,290,615 discloses a new golf ball which has, in place of conventional dimples, a number of small hexagonal segments divided by thin ridges extending in a lattice pattern on the smooth spherical surface.
However, such small hexagonal segments (which are not dimples) constitute the spherical surface whose center coincides with the center of the golf ball. Therefore, they do not reduce aerodynamic resistance so effectively.